1. Technical Field
The present invention relates to a machine tool that performs position and dimension measurements of a workpiece.
2. Background Art
In machine tools, a touch probe (touch sensor) is attached to a main axis thereof to perform position measurement for positioning a workpiece and dimension measurement of a workpiece during setup or the like. A touch probe includes a stylus serving as a measuring element. Such touch probes are categorized into a contact point signal type in which a stylus is inclined by coming into contact with a surface to be measured to thereby change a mechanical contact point and a touch signal type that detects a state in which a stylus touches and is in contact with a surface to be measured, thus establishing electrical connection with the surface to be measured. With the measurement performed by either type of touch probe, a touch probe and a workpiece are moved relative to each other in a direction in which the stylus approaches the surface to be measured to thereby bring the stylus in contact with the surface to be measured of the workpiece, and measurement of the position and dimension of the workpiece is performed by reading NC coordinates at this contact time (see JP 8-313242 A, for example).
In a method of performing measurement of the position and dimension of a workpiece by a touch probe as described in JP 8-313242 A, because the touch probe moves linearly, there are cases in which it is not possible to perform measurement of the shape of a surface of a workpiece having a small radius of curvature and a surface of a spherical workpiece. In order to address these disadvantages, there is suggested a method in which a touch probe is, for example, attached to a main axis and performs simultaneous multi-axis measurement including a linear drive axis and a rotation axis by bringing the same tip end point of the touch probe in contact with the surface of the workpiece (see JP 2010-32373 A).